Variable-speed safety-valve.



-Nm 7|7,08l. Patented Dec. 30, |902.

M. CURHINGTON. VARIABLE SPEED SAFETY VALVE.

(Application Bled June 27, 19023 (Nn Modal.)

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Unrrnp Srafrns Parietti OFFICE.

MURRAY OORRINGTON, OF NEW YORK, N. Y.

VARIABLE-SPEED SAFETY-VALVE.

SPECIFICATION forming part of Letters Patent No. 717,081, dated December 30, 1902. Application filed June 27.1902. Serialllo.113,393. (No model.)

Sl'o @ZZ whom it may concern.:

Be it known that 1, MURRAY CORRINGTON, a citizen of the United States, residing at New York city, in the county and State of New York, have invented certain new and useful Improvements in Variable Speed Safety Valves, of which the following is a specification.

My invention comprises a novel type of variable-speed safety-valve device.

An ordinary safety-valve is usually so arranged that it will remain closed and prevent the escape of pressure to a certain degree and will then open a port of a given size and allow the excess pressure to escape at a practically uniform rate of speed-that is to say, the excess pressure will decline a given number of degrees in equal periods of time. For instance, if the pressure drops two pounds in one second it will drop four pounds in two seconds, and so on until the excess pressure is relieved and the safety-valve closes.

My invention embodies what I term a variable-speed safety-valve device, and by this I mean a device which is adapted to retain a given amount of pressure in the vessel to which it is attached, and whenever a considerable eX- cess pressure is suddenly admitted to the vessel the device will open and begin to release this excess pressure at a given rate of speed, and as time elapses and the pressure declines the rate of speed at which the pressure is released will vary during succeeding periods of time, either at an increasing or at a decreasing rate.

Figure l is a vertical section illustrating my invention in one of its forms. Fig. 2 is asimilar section of myinvention in a slightlymodified casing, showing its application to a brake-cylinder forming part of an air-brake system. Fig. 3 is a vertical section of my invention for releasing pressure at a decreasing rather than an increasing rate. Fig. 4 is a slightly-enlarged section of the bush of the piston-chamber, showing a modified arrangement of ports.

Fig. 1 embraces a main section of casing 6, having a flange for attachment to a suitable support and a piston-chamber lO, with a bushing 21 and a piston 12 operating therein. A spring 13, surrounding the piston-stem 11, bears upon the under side of the piston -by the cap-nut 52.

12 and is adjusted to lthe desired tension by the nut 15, which may be covered and locked These parts are inclosed within 'a casing-section 16, which is appropriately fastened to the case 6. 'A gasket 50 on. the upper side of piston 12 is held in place by a nut 5l and its edges bear upon projecting shoulders of the bush 21, thus making an air-tight joint. The port 7 is for connection with any suitable chamber or vessel holding fluid under pressure to which this safety-valve device is to be attached. The bush 2l has'a port 54 at the upper end of the piston-chamber and a series of ports 5G below said piston, while a passage connects these ports. Port 53 leads from the chamber 10 to the atmosphere.

The operation of the device is as follows: The spring 13 is adjusted to hold the piston `in the position shown, with the gasket 50 against the shoulders of the bushing 2l, so long as the pressure admitted above the piston through the passage 7 does not-exceed a given amount. If a'slight excess pressure is admitted through the passage 7, the piston moves downward a short distance against the spring 13 and permits this slight excess pressure to flow out through the ports 511, 55, 56, and 53 to exhaust. It a considerable excess is suddenly admitted to the passage 7, the piston Y12 moves downward quickly until it rests against the top of casing 16, at which time the packingring of the piston 12 stands be- Vlow or covers all of the series of ports 56 excepting the lowest one. Pressure coming through the passage 7 flows through 54 55 and the lowermost of the ports 56 and thence to exhaust very slowly, thus causing a very moderate reduction in the chamber 7. As the pressure falls sufficiently the spring 13 moves the piston 12 upward a small distance and uncovers the second port 56, thus increasing the rate of expansion of the pressure above the piston. This causes a further reduction above the piston and permits the spring to move the piston upward far enough to uncover the third port 5G, making the reduction of pres- ,sure above the piston that much more rapid.

As the spring continues to move the piston back toward normal position the rate of reduction of the pressure above the piston increases as one after another ofthe ports 56 IOO is placed below the piston. If we suppose that the ports 56 are all the same size, then it is evident that when the piston uncovers two of the ports 56 the decrease in the pressure above the piston will be twice as rapid as when only one of those ports is uncovered, and when four of the ports are uncovered it will be four times as rapid as when only one is open. Of course the size of the ports 56 may increase from the bottom toward the top. The port 54 likewise may be very narrow, as shown in Fig. 4, and extend around the bush. It should preferably be about as large as the capacity of all the ports 56. Essentially the same results will follow if the partitions between the ports 56 are removed.

From the description of Fig. 1 corresponding parts of Fig. 2 will be readily recognized from their corresponding numbers, and their functions will be readily understood. The device is shown as applied to the head of an ordinary brake-cylinder 4, which is a part of an air-brake system. It is common' in airbrake practice to ordinarily operate the system with such pressure that when the brakes are applied in what is known as an emergency application the resulting pressure in thebrake-cylinder is about sixty pounds per square inch. At the same time it is often desired when the trains are running at very high speed to operate the brake system with such pressures as will give about eightyive pounds pressure in the brake-cylinder in the emergency action, and this must be reduced gradually to the ordinary emergency pressure of sixty pounds in order to prevent the sliding of wheels. In this use of my device, therefore, the spring 13 is adjusted to balance about sixty pounds on the upper side of the piston 12. When the brake system is operated with about one hundred pounds pressure on the cars and the brakes are applied in emergency, we shall have a resulting pressure in the brake-cylinder 4 of perhaps eighty-live pounds, which will instantly be communicated to the piston 12, forcing it downward until itrests against the lower casing-section 16. As already explained in connection with Fig. 1, the packing-ring of the piston passes below or covers all the ports 56 excepting the lowest one. This permits a reduction of pressure through port 54, passage 55, and the lowest of ports 56, which is very moderate at first 5 but as the pressure declines suiiciently the spring 13 gradually moves the piston back to its normal position, uncovering one after another of the ports 56,and thus gradually increasing the rate of reduction of pressure in the brake-cylinder 4. A groove 57, narrow at the bottom and wider at the top,may

I be cutin the bush 2l,to be employed either sepquite narrow and extending around the bushing, while the ports 56 arearranged in trianguiar shape. This arrangement of ports would effect a still greater increase in the rate of reduction of pressure as the piston moves from its lowest back to normal position.

In Fig. 3 the same parts essentially are arranged in the same relationship and operate in the same manner by means of pressure suddenly admitted through the passage 7. The effect produced,however,by the operation of the piston is exactly the opposite of that produced by Figs. 1 and2, because the ports 54 and the ports 56 have in this figure changed places. When an excess pressure is suddenly admitted above the piston 12, it moves downward, as before, against the lower casing-section 16, placing all of the ports 56 above the piston, while the port 54 remains below. The pressure above they piston therefore Hows out rapidly through all of the ports 56 into 55 and thence by 54 and 53 to exhaust, thus causing a rapid reduction of pressure. As the pressure above the piston declines and the spring 13 moves the piston upward toward normal position it passes above the ports 56 one after another until they are all closed, thus gradually diminishing the rate of iiow from the chamber above the piston.

I am aware of other forms of variable-speed safety-valve devices and of their use in connection with brake-cylinders, in which the combination of a piston and a Valve is employed to produce the desired result; but it is the characteristic of my within-described invention that I wholly abandon the use of a valve and rely upon the piston operating in its chamber alone and by itself to accomplish the result, and I desire that the annexed claims shall be construed with this fact in mind.

I claim- 1. In asafety-valve device,the combination of a piston in a chamber open on one side to fluid under pressure, a load on the other side of said piston balancing a given or normal pressure on the opposite side and means arranged in the wall of the piston-chamber and controlled by said piston for permitting a considerable excess of pressure to escape past the piston at a continuously-varying rate of speed as the load returns the piston toward its normal position.

2. In a safety-valve device,tl1e combination of a piston in a chamber open on one side to iluid under pressure, a load ou the other side of said piston adapted to balance a given definite pressure on the opposite side and means arranged in the wall of the pistonohamber and controlled by the movement of said piston for permitting a considerable excess of pressure to escape past said piston, slowly at first and then at an increasing rate of speed as the load returns said piston toward its normal position.

3. In a fluid-pressure brake system, the combination7 with a brake-cylinder, of a pis- IOO IIO

ton-chamber, a passage for permitting the pressure to escape from said cylinder through said piston-chamber, a piston in said chamber carrying a load adapted to hold it in position to close said passage when 'a given 0r normal pressure is admitted to said cylinder and means arranged in the wall of the chamloer and controlled by said piston so constructed that, when an extraordinary pressure is suddenly admitted into said cylinder, it will escape slowly at first and then at an increasing rate of speed as the piston is returned by the load toward its normal position.

4. In a fluid-pressure brake system, the combination, with a brake-cylinder, of a piston-chamber, a passage for permitting the pressure to escape from said cylinder through said piston-chamber, a piston in said chamber, a spring bearing on said piston and adjusted to hold it in position to close said passage against a given, definite pressure admitted to said cylinder, and means so arranged in the wall of the chamber and controlled by said piston that, When a considerable excess pressure is admitted into said cylinder, the spring yields and the piston permits the pressure to escape slowly and, as the pressure falls and the spring returns the piston toward normal position, the pressure escapes at an increasing rate.

MURRAY CORRINGTON. Witnesses:

BURTON E. EMORY, FAUSTINO S. ALVAREZ. 

